Catalytic igniters for combustion equipment



y 1965 B. TOONE ETAL 3,182,472

CATALYTIC IGNITERS FOR COMBUSTION EQUIPMENT Filed Dec. 2, 1965 fi- -9 H United States Patent 3,182,472 CATALYTIC IGNITERS FOR COMBUSTHGN EQUIPMENT Brian Toone, Littleover, Derby, England, and Allan M.

Barham, Pennard, Swansea, Wales, assignors to Relis- Royce Limited, Derby, England, a company of Great Britain Filed Dec. 2, 1963, Ser. No. 331,077 Claims priority, application Great Britain, Dec. 14, 1962, 47,374/ 62 12 Claims. (Cl. 67-19) This invention concerns prime mover ignition devices for promoting ignition of fuel injected into a stream of combustion-supporting gas, and although not so restricted, the invention will be described hereinafter, with reference to its use in gas turbine engines.

According to the present invention there i provided a prime mover ignition device for promoting ignition of fuel injected into a stream of combustion-supporting gas, said device comprising a plurality of substantially cylindrical foraminate rolls of platinum, or rhodium, or platinumrhodium alloy or other metal or alloy having catalytic properties in the promotion of combustion, said rolls being supported, in an annular formation, by a mass of refractory material, the said mass having at least one flow passage extending through it to lead combustion mixture to the said rolls.

The substantially cylindrical rolls may touch one another, and may be of spiral cross-section.

Preferably, the rolls are disposed within an annular space formed between the wall of a cylindrical hole in said mass and a supporting cylinder concentrically mounted within the cylindrical hole in said mass. The cylindrical hole may form a part of said flow passage.

The supporting cylinder is preferably formed of a gauze of catalytic metal or alloy. Thus the gauze may be made of an alloy of platinum and rhodium, the rhodium constituting from -30% of the alloy.

Preferably the end faces of said substantially cylindrical rolls are covered with or situated closely adjacent upstream and downstream end plates formed of a catalytic metal or alloy. The upstream plate may be formed of platinum/rhodium gauze, the downstream plate being a solid plate of a platinum alloy.

In a preferred embodiment, the fuel/air mixture to be ignited is fed directly into a catalytic zone adjacent said rolls. Preferably, the upstream end of said mass of refractory material is provided with a plurality of apertures which lead directly into the interiors of said substantially cylindrical rolls.

The invention also include a gas turbine engine provided with an ignition device as set forth above.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which:

FIGURE 1 is an elevational view of two prime mover ignition devices according to the present invention,

FIGURE 2 is a cross sectional elevation of the device shown in FIGURE 1 taken on the line 22 of that figure, and

FIGURE 3 is a cross sectional elevation of the device shown in FIGURES l and 2 taken on the line 33 of FIGURE 2.

Referring to the drawings, there is shown a housing 10 of refractory material, constituting parts of two identical prime mover ignition devices 8 and 9. Since the devices are identical, only one will be described in detail hereinafter. The refractory material for the housing 10 must have good strength at high temperatures and good thermal shock characteristics. Silicon nitride, silicon carbide or a combination of these are preferred refractory materials for the housing 10. A flow passage 11 extends through 3,182,472 Patented May 11, 1965 the housing 10, and is enlarged along a substantial portion of its length to form a cylindrical hole 12.

Disposed within the cylindrical hole 12, adjacent an end 13 thereof, is a ring 14 of refractory material such, for example, as silicon-free alumina. Lining the remainder of the cylindrical hole 12 is a sleeve 15 of refractory material such, for example, as silicon-free alumina. Siliconfree alumina is used to reduce contamination of the catalyst (described hereinafter) with silicon.

Disposed within the cylindrical hole 12, and aligned with the flow passage 11 is a supporting cylinder 16. This supporting cylinder is formed of a platinum/rhodium .alloy gauze containing 20% rhodium. The supporting cylinder 16 has an internal diameter substantially equal to the diameter of said flow passage 11, and is spaced from the sleeve 15 by an annular space.

Disposed within this annular space are ten cylindrical rolls 20 of gauze formed of a platinum/rhodium alloy containing 20% rhodium. The size of the cylindrical rolls 20 in relation to the size of the annular space is such that the cylindrical rolls are held between the supporting cylinder 16 and the sleeve 15, and adjacent rolls 20 touch one another. Thus, vibration of the cylindrical rolls 20 within the annular space is reduced to a minimum.

Covering the open ends of the cylindrical rolls 20 are an'upstream plate 21 and a downstream plate 22. The upstream plate 21 is a circular disc of gauze made from platinum/rhodium alloy comprising 20% rhodium. The downstream plate 22 is a solid ring of, for example, platinum-rhodium alloy comprising 20% rhodium. The downstream plate 22 may, in fact, be made of any alloy of platinum, since it does not have any catalytic effect, but must merely be such as to Withstand the high ambient temperatures.

The housing 10 has an upstream face 24 to which is attached a perforated plate 25 formed of a refractory material such, for example, as silica-free alumina. The perforated plate 25 is rectangular, as seen in FIGURE 1, and has formed therein a central hole 26 and six equispaced holes 27. The hole 27 are disposed on the same pitch circle as the centres of the ten cylindrical rolls 20.

In use, the ignition device is disposed in a gas stream of fuel and air, with the stream flowing from left to right, as seen in FIGURE 2. The fuel/air mixture flows through the central hole 26, and, through the supporting cylinder 16 and flow passage 11. The fuel/air mixture also flows through the six holes 27 and directly into the interiors of said cylindrical rolls 2!). Thus the fuel/air mixture is fed directly to the'catalytic zone which is ad-, jacent said rolls. The fuel/ air mixture then flows through the remainder of the flow passage 11 and passes out of the device.

In passing through the ignition device, the fuel/ air mixture is ignited due to the catalytic action of the device.

When adapted for use in the reheat combustion equip ment of a gas turbine engine, the housing 10 is provided with grooves 30 to enable it to be held in place by, for example, corresponding ribs on the sides of a V-section stabilising gutter (not shown).

A particularly useful and eflicient ignition device has been produced using the following dimensions, which are approximate:

Ins. Overall length of cylindrical rolls 20 0.750 Diameter of cylindrical rolls 20 0.125 Thickness of cylindrical rolls 20 0.010 Diameter of flow passage 11 0.375 Thickness of supporting cylinder 16 0.020 Thickness of upstream plate 21 0.020 Thickness of downstream plate 22 0.010 Diameter of central hole 26 0.187 Diameter of six holes 27 0.094 Internal diameter of sleeve 15 0.750

snsaava any foraminate material of platinum/ rhodium alloy may be used. Thus, the supporting cylinder 16 could be made of 0.030 in. thick expanded metal. A few tests carried out on an ignition device with such a supporting cylinder indicatedthat such devices give better results at 0.5 Mach Whilst having increased mechanical strength.

. Again, the supporting cylinder 16' could be drilled from solid platinum/rhodium alloy, and have a plurality of holes. drilled in its sides. loy containing 40% rhodium may be used, so increasing the strength and melting point'of the cylinder. However, the catalytic activity of the cylinder is reduced in this case. catalysts are those formed from platinum/rhodium alloys containing from 10-30% rhodium. As indicated above, a higher percentage of rhodium can be used toob- With this arrangement, an 211- Generally, it has been found that the most useful tain increased strength, but only at the expense of cata- I lyticactivity.

It will also be appreciated that, as a further modifica tionof the embodiment described above, the cylindrical rolls 20- could be constructed to have a spiral cross section.

We claim: a

l. A prime mover ignitiondevice for promoting ignition of liquid fuel injected into a stream of combustion supporting gas, said device comprising a plurality of substantially cylindrical foraminate'rolls of a material having catalytic properties in the promotion of combustion, a mass of refractory material provided with'a cylindrical hole, a supporting cylinder of gauze of a catalytic material concentrically mounted Within'said cylindrical hole and defining therein an annular space; said rolls being arranged in annular formation, withinsaid annular space, and an upstream end of said mass of refractory material provided withza plurality of apertures through which a combustion mixture may. fiow directlyinto theinterior of saidrolls;

6. A'device as claimed'in claim 5 in which said gauze is made of an alloy of platinum and rhodium, the rhodium constituting 10-30% of the alloy.

7. A prime mover ignition device for promoting. ignition of liquid fuel injected into a stream of combustion supporting gas, said device comprising a plurality of substantially cylindrical foraminaterolls of a r'naterial having catalytic properties in the promotion of combustion, upstream and downstream end plates formed of a catalytic material covering end faces of said rolls,'a mass of refractory material supportingsaid rolls in an annular formation, said, upstream end plate being provided with a plurality of apertures through which a combustion mixture may flow directly into the interior of said rolls.

8. Aprime mover ignition device for promoting ignition of liquid fuel injected into a stream of combustion supporting gas, said device comprising a plurality of substantially cylindrical foraminate rolls of a material having catalytic properties in the promotion of combustion, an upstream end plate of platinum/rhodium gauze and a downstream solid end plate of platinumalloy covering end faces'of said rolls, a mass of refractory material supporting said rolls in an annular formation, said upstream end plate being provided with a plurality of apertures through which a combustion mixture may flow directlyinto the interior of said rolls. 7

ing catalytic properties inthe, promotionof combustion,

amass of refractory material supporting said rolls in an annular formation with adjacent rolls touching one another, and an upstream end of said mass of refractory material provided with a plurality of apertures through which a combustion mixture may flow directly into the interior of said rolls.

2; Aprime'mover ignition device for promoting ignition of liquid fuel injected into a stream of combustion I supporting gas, said device comprising a plurality of substantially cylindrical foraminate rolls of spiral cross section and made of a material having catalytic properties in the promotion of combustion, a mass of refractory material supporting said rolls in an annular formation,; and an upstream end of said mass of refractory material provided with a plurality of apertures through which a combustion mixture may flow directly into the interior of said'rolls.

cal hole, a supporting cylinder concentrically mounted,

within said cylindrical hole and defining therewith an annular space, said rolls being arranged in annular formation within said annular space, and an upstream end.

of said mass of refractory material provided with a plurality of apertures through which a combustion mixture may flow directly into the interior of said rolls.

4. A device as claimed in claim 3 in which said cylindrical hole forms a part of said flow passage.

5. A prime mover ignition device for promoting ignif tion of liquid fuel injected into a stream of combustion supporting gas, said device comprising a plurality of substantially cylindrical foraminate. rolls of a material hav- 9. A prime mover ignition device. for promoting ignition of liquid fuel injected intoa stream'of combustion supporting gas, said device comprising a plurality of substantially cylindrical foraminate rolls of a material having catalytic properties in the promotion of combustion, a mass of refractory material supporting said rolls in an annular formation, and forming a catalytic zone, and an upstream end of said mass of refractory material provided with a' plurality of apertures through which a combustion mixture may-flow directly into the interior of said rolls.

10. A prime mover ignition. device for promoting igni-' 11. An ignition device comprising aplurality of sub-' stantially'cylindrical foraminate rolls of a material having catalytic properties in the promotion of combustion,

a massof refractory material supporting said' rolls in an annular formation, and an upstream end of said mass of refractory material provided with a plurality of apertures throughwhich a. combustion mixture. may flow directly into the interior ,of said rolls.

12. A high strength'prime mover ignition device for promoting rapid ignition of a high speed, high pressure combustion mixture of liquid fuel injected into a stream of combustion supporting gas comprising: a housing of refractory material having aniupstream end, a downstream endiand a generally cylindrical.cavitycxtending between said upstream end and said downstream end; a foraminate cylinder of a material having catalytic properties in the promotion of combustion mounted concentrically within said cavity and defining an annular space between the wall of said cavity and said cylinder; 0. plurality of generally cylindrical elongated forarninate rolls of a material having catalytic properties in the promotion of combustion, said rolls being arranged in generally coextensive relationship in said annular space and in contact with each other and with said cylinder and with the wall of said cavity, the upstream end of said housing having a plurality of apertures through which a combustion mixture may flow directly into said cavity and directly into the interior of said rolls, the downstream end of said housing being closed adjacent the ends of said rolls and having an outlet flow passage adjacent the end of said cylinder whereby a combustion mix- 6 ture may flow from the interior of said rolls through the walls of said rolls into said cylinder and out of said housing through said flow passage.

References (Jited by the Examiner UNITED STATES PATENTS EDWARD J. MICHAEL, Primary Examiner. 

1. A PRIME MOVER IGNITION DEVICE FOR PROMOTING IGNITION OF LIQUID FUEL INJECTED INTO A STREAM OF COMBUSTION SUPPORTING GAS, SAID DEVICE COMPRISING A PLURALITY OF SUBSTANTIALLY CYLINDRICAL FORAMINATE ROLLS OF A MATERIAL HAVING CATALYTIC PROPERTIES IN THE PROMOTION OF COMBUSTION, A MASS OF REFRACTORY MATERIAL SUPPORTING SAID ROLLS IN AN ANNULAR FORMATION WITH ADJACENT ROLLS TOUCHING ONE ANOTHER, AND AN UPSTREAM END OF SAID MASS OF REFRACTORY MATERIAL PROVIDED WITH A PLURALITY OF APERTURES THROUGH WHICH A COMBUSTION MIXTURE MAY FLOW DIRECTLY INTO THE INTERIOR OF SAID ROLLS. 